Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
  • H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
  • H03J7/18—Automatic scanning over a band of frequencies
  • H03J7/183—Automatic scanning over a band of frequencies combined with selection between different stations transmitting the same programm, e.g. by analysis of the received signal strength
  • H03J7/186—Automatic scanning over a band of frequencies combined with selection between different stations transmitting the same programm, e.g. by analysis of the received signal strength using two or more tuners
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
  • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
  • H03J1/0008—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor
  • H03J1/0058—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor provided with channel identification means
  • H03J1/0083—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor provided with channel identification means using two or more tuners
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04H—BROADCAST COMMUNICATION
  • H04H2201/00—Aspects of broadcast communication
  • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
  • H04H2201/13—Aspects of broadcast communication characterised by the type of broadcast system radio data system/radio broadcast data system [RDS/RBDS]

Definitions

• the invention relates to a method for selecting a tuning frequency for receiving an RF transmitter within an RF frequency band and an FM receiver executing the method.
• An FM receiver executing the above method is on itself known e.g. from European Patent 0 333 194.
• the known FM receiver complies with the FM RDS broadcasting standard as defined m "Specification of the Radio Data System FM RDS for VHF-FM Sound Broadcasting' by the European Broadcasting Union (EBU) , EBU document Tech 3244 -E, March 1984 and updated m the subsequent revisions thereof .
• EBU European Broadcasting Union
• the cited FM receiver comprises a first or stationary tuner circuit and a second or scanning tuner circuit.
• the stationary tuner circuit s used to tune the receiver to a broadcast transmitter station with a wanted audio program, hereinafter indicated as first transmitter frequency, and to process the audio program signals for sound reproduction. If the transmitter transmits RDS data as well, then the stationary tuner circuit will also extract the RDS data carried by the received RDS transmitter signal, m particular a list of alternative frequencies (AFs) . Such list provides tuning data of transmitters carrying the same program as the one the stationary tuner circuit is actually tuned to.
• the scanning tuner circuit is used to monitor the reception quality of the transmitter signals at each of those AFs.
• the scanning tuner circuit is sequentially switched to each AF m the AF list to measure the fleldstrength of the transmitter signals at the respective AFs.
• the fleldstrength information is stored m a memory and repeatedly updated m sequential scan cycles.
• first transmitter frequency On deterioration of the received stationary transmitter signal, hereinafter indicated as first transmitter frequency, the stationary tuner circuit s automatically switched over m its tuning from said first transmitter frequency to another transmitter frequency, hereinafter indicated as second transmitter frequency.
• the AF stored m the memory having highest fleldstrength is chosen to be such second transmitter frequency.
• the reception quality measurement is based on the momentary fleldstrength of the RF FM reception signal and the AF having highest fleldstrength at the moment of tuning switch over may lose this position very quickly , due to fluctuations m the environmental reception conditions. This may cause instabilities m the tuning of the receiver.
• the selection of a second transmitter frequency is limited to tr-e AFs included m the RDS AF list, being alternative frequencies carrying the same audio program as the first transmitter frequency.
• An object of the invention is to improve the tuning behaviour of the above mentioned receiver.
• a method for selecting a tuning frequency for receiving an RF transmitter within an RF frequency band is characterized by a band scanning search for detecting transmitters exceeding a predetermined reception quality level, by storing the tuning data thereof and allocating thereto a permanency factor indicating the permanency m reception quality thereof, said tuning frequency being selected on the basis of at least said permanency factor.
• An FM receiver executing the method according to the invention comprising first and second tuner circuits respectively for receiving a first FM transmitter and for detecting in an FM band FM transmitters received with a reception quality exceeding a predetermined quality threshold level, and storage means for storing the tuning data of the so detected FM transmitters, the first tuner circuit switching over from an actually received first FM transmitter to a second FM transmitter selected from the detected FM transmitters when the reception quality of the first FM transmitter decreases below a predetermined level, is therefore characterized by a processing unit: allocating to each detected FM transmitter a permanency factor indicating the permanency m reception quality thereof, said selection of the second FM transmitter being based on at least said permanency factor.
• the criteria for selecting a second transmitter are not only based on the reception quality or fleldstrength thereof, but also on the duration or permanency of the reception quality.
• the method is preferably characterized m that the band scanning search is being repeated m subsequent scan cycles, each detected transmitter increasing respectively decreasing m permanency factor dependent on the detection respectively the absence of detection thereof m subsequent scan cycles.
• An FM receiver executing said preferred method is characterized by tuning control means controlling the tuning of the second tuning circuit to repeat the band scanning search m subsequent scan cycles, the processing unit increasing, respectively decreasing, stepwise the permanency factor of a transmitter at each detection, respectively m the absence of detection, thereof in a subsequent scan cycle.
• the tuning data of transmitters having a permanency factor decreasing below a predetermined permanency threshold level are being erased to exclude such transmitters from being selected.
• An FM RDS receiver executing said preferred method is characterized m that the storage locations of tuning data relating to transmitters decreasing in permanency factor below a predetermined permanency threshold level, being released for storage of other transmitter data.
• This measure further improves the efficiency in the use of memory capacity without losing the information which transmitter frequency should be chosen in case the actually received transmitter signal decreases below said predetermined threshold level .
• the band scanning search will reveal all transmitters in the FM band meeting the minimum reception quality requirement. This allows to apply said selection of the second transmitter frequency also when changes in the audio program are permitted or wanted.
• such second transmitter frequency may carry an audio program signal different from the actually received one, but falling e.g. within the same PTY category, and/or including traffic messages. The selection is therewith PTY determined.
• RDS program codes may be used for the identification of such audio programs.
• the processing unit repeatedly monitors the permanency factor of the FM transmitters carrying an audio program within the same PTY category as the audio program of the first FM transmitter.
• the second transmitter is selected from FM transmitters carrying traffic messages on the basis of fieldstrength in addition to the permanency factor.
• the processing unit operates to monitor the permanency factor of FM transmitters carrying traffic message information as well as the fieldstrength thereof, the second FM transmitter being selected from the detected FM transmitters upon receiving a traffic announcement signal on the basis of fieldstrength m addition to the permanency factor.
• the fleldstrength is used in this measure to identify the nearest transmitter sending traffic messages, which are most relevant to the actual location of the user because of the proximity of the transmitter.
• Figure 1 a blockdiagram of a dual tuner FM RDS receiver according to the invention
• Figure 2 an organisational scheme of the list of transmitter related data as stored m the FM RDS receiver of Figure 1 ;
• FIG 3 a flowchart illustrating the method according to the invention as being executed by the FM RDS receiver of Figure 1.
• FIG. 1 shows a blockdiagram of an FM receiver according to the invention, which m the preferred embodiment as shown complies with the FM RDS broadcasting standard as defined m above cited EBU document. Reference is made to this document for detailed information on the meaning and definition of the various terms and abbreviations relating to the RDS standard, as mentioned hereinafter.
• the FM receiver receives RF FM signals through an antenna 1 and following this antenna 1, it comprises first and second tuner circuits 2 and 3, the tuning frequency thereof being controlled from tuning control means 10, 11, 25.
• the tuning control means 10, 11, 25 comprise a central processing unit (CPU) 25 and an I/O control module 11 being included in a microprocessor 12 and connected through a control bus 10 to the first and second tuner circuits 2 and 3.
• CPU central processing unit
• I/O control module 11 being included in a microprocessor 12 and connected through a control bus 10 to the first and second tuner circuits 2 and 3.
• Key 21 is to activate an autostore functionality
• key 22 is to activate an up/down search
• key 23 is to switch on/off the reception of traffic messages
• key 24 is to activate a search for programs within the same PTY category as the one actually received.
• These functionalities require the use of a program memory 26 for the storage of program software and a timer module 28 and are on themselves already known from e.g. the FM RDS radio receiver type VDO RC 959 RDS.
• the first tuner circuit 2 provides for the stationary selection and demodulation of a wanted RF FM broadcast signal into baseband and comprises means to measure the reception quality of the received FM RF signal.
• a quality factor reflecting said reception quality is supplied via a quality level line 14 to an AD converter module 15 of the microprocessor 12 to be further processed as described hereinafter.
• the baseband FM modulation signal may comprise an RDS signal and/or a mono or stereomultiplex signal.
• This baseband signal is supplied via a signal line 5 from an output of the first tuner circuit 2 to a digital signal processor 6.
• the digital signal processor 6 comprises audio signal processing means (not shown) to process mono audio signals and eventually demultiplex stereomultiplex signals into stereo left and right audio signals. These stereo left and right audio signals are supplied to an audio amplifier 8 and subsequently to a stereo loudspeaker set 9 for respectively amplification and reproduction thereof.
• the digital signal processor 6 is coupled to an RDS decoder 7 to decode RDS data contained m the received FM broadcast signal.
• the decoded RDS data are supplied via an RDS data line 18 to an RDS data I/O module 19 of the microprocessor 12.
• RDS data processing occurs under control of the CPU 25 of the microprocessor 12.
• the tuning frequency of the second tuner circuit 3 is automatically varied by the tuning control means 10, 11, 25 to scan over the full RF FM broadcast reception band ranging from 87.5 MHz to 108 MHz, starting from e.g. the lower end of said RF FM band.
• the scanning operation will be interrupted upon first reception of an FM broadcast station fx having a signal reception quality exceeding a certain predetermined threshold level qt (hereinafter also indicated as scan hit) .
• qt a certain predetermined threshold level
• measurement, processing and storage steps are being made under control of the CPU 25, as described m the following with reference to Figure 2.
• the tuning data of fx is stored at a storage address Tx of a data memory 27 of the microcontroller 12;
• a permanency factor px is being allocated to fx, set at unity value and stored at Tx; 3. the actual reception fieldstrength is measured and a fieldstrength factor sx reflecting said reception fieldstrength is stored at Tx;
• An RDS decoder 4 following the output of the second tuner circuit 3 is to extract RDS data from the demodulated RDS signal, if fx is carrying such RDS data.
• the RDS data is supplied via an RDS data line 16 to an RDS data I/O module 17 of the microprocessor 12 and the various program related RDS codes included therein, such as e.g.
• the PTY- , TA- , TMC- , PS-, and/or PS Mask codes are stored m said data memory at the storage address Tx of fx.
• an RDS flag identifying RDS transmitters with value 1 and non-RDS transmitters with value 0 may be stored m TX as well.
• the above measurement, processing and storage steps are repeated for fy, the tuning data thereof, as well as a permanency factor py and a fieldstrength factor sy, eventually along with RDS program data are being stored m the data memory at storage address Ty .
• These steps are repeated for each such FM broadcast station until the full RF FM broadcast reception band has been scanned, whereafter the scanning operation is repeated, either m the same or m reversed scan direction.
• the reception quality may be based on one or more parameters, such as e.g. the reception fieldstrength, the (lack of) multipath and other environmental sources of pollution.
• the above predetermined threshold level qt is chosen such, that RF FM broadcast signals exceeding this level can be processed properly without giving rise to receiver malfunctioning and/or noticeable signal distortions .
• Said known receiver also provides a reference for the measuring of the actual reception fieldstrength of certain transmitters and the storage of a fieldstrength factor sx reflecting said reception fieldstrength, the retrieval of various program related RDS codes included m the received RF FM signal, such as e.g. the PTY, TA- , TMC-, PS-, and/or PS Mask codes and the storage of these data m a data memory at storage addresses related to the relevant transmitter frequencies.
• various program related RDS codes included m the received RF FM signal, such as e.g. the PTY, TA- , TMC-, PS-, and/or PS Mask codes and the storage of these data m a data memory at storage addresses related to the relevant transmitter frequencies.
• px will decrement with unity value, each time a subsequent scan appears to be empty on fx.
• the second tuner circuit 3 of the FM receiver collects not only transmitter data of AFs only, but of all transmitters exceeding the predetermined reception quality level qt .
• This allows to offer the user a broader range of options m automatically selecting audio programs. For instance, by activating the "autostore' option with key 21, the fieldstrength factor of the various transmitters stored m the data memory may be compared with a certain threshold level, chosen such that it is exceeded by only a limited number of transmitters (e.g. 10), which can be RDS- or non-RDS transmitters .
• the tuning data of these transmitters are stored m the autostore memory and called up by touching the key 21.
• the threshold level may based on a predetermined threshold value for the permanency factor, eventually m combination with a predetermined threshold value for the fieldstrength factor. This also applies to the threshold level for use m the up/down search of transmitters, which feature can be activated with key 22.
• the various program related RDS codes like PTY, TP and TA are used to offer the user options m automatically selecting within the category of programs indicated therewith, the best receivable transmitter from those having these codes stored m the data memory of the receiver.
• the receiver can be set to reproduce traffic messages.
• the criterium to select an appropriate traffic message transmitting RDS broadcast station amongst those carrying the traffic announcement flag is based on the permanency factor, i.e. the best to receive RDS traffic message broadcast station having the highest permanency factor. If the highest permanency factor is shared by various transmitters, then the fieldstrength factor may additionally used to come to the one best to receive. The transmitter received strongest (i.e. with highest fleldstrength) is m practise nearest to the receiver location and the traffic messages of that transmitter are therewith most relevant to the user.
• FIG. 3 shows a flowchart of an algorithm for collecting and updating transmitter and RDS program related data to be used m a method for tuning the reception of radio broadcast signals to an FM transmitter m accordance with the invention, m which steps al-al5 have the following meaning : al Switching on the radio and starting the method according to the invention. for selecting a tuning frequency for receiving an
• the second tuner circuit 3 is initialised for starting a scan cycle from the lower end of the FM frequency band at 87.5 MHz.
• the data memory 27 is initialised for transmitter and RDS program related data storage .
• the tuning frequency of the second tuner circuit 3 is being increased to scan the FM and interrupted upon reception of a transmitter fx. During an interruption period the signal reception quality (this can be the fieldstrength or other parameters defining the reception quality level) of fx is measured. In the following the fieldstrength is taken as a measure for the reception quality.
• the data memory 27 therewith contains at any time the most recent status of the receivable transmitters in the FM band in terms of momentary reception quality or fieldstrength sx and permanency or stability of reception quality px.
• the continuous availability of the abovementioned transmitter related data in an FM receiver according to the invention allows to determine immediately which transmitter within the FM band provides optimal reception conditions, i.e. which transmitter within the FM band has highest permanency factor px. If the highest px value is shared by several transmitters, then the fieldstrength factor sx may be taken additionally to determine the best to receive transmitter.
• the availability of program related RDS data allows to restrict the group of transmitters to be considered for the above determination of the best to receive transmitter.
• the group of transmitters to be considered for the above determination in case the user is interested m any audio program within a certain PTY category is limited to those transmitter carrying the RDS PTY code of said category. Accordingly, m determining the best to receive traffic message broadcast transmitter station, use can be made of the RDS TA code to limit the group of transmitters to be considered therefor.
• the invention is not restricted to the embodiments described above and may well be used m e.g. a non-RDS receiver for implementing an "autostore' functionality, wherein a number of strongest transmitters are being stored under a same number of tuner preselection keys.
• the functions of the first and second tuner circuits 2 and 3 may well be performed with a single tuner, m which the stationary reception is repeatedly shortly interrupted to allow the tuner during each interruption period to scan through a part of the FM band covering the whole FM band after a number of interruption periods.

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• Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Circuits Of Receivers In General (AREA)
• Channel Selection Circuits, Automatic Tuning Circuits (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

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Family Applications Before (1)

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• 1999
  • 1999-05-26 EP EP99200525A patent/EP1056203A1/de not_active Withdrawn
• 2000
  • 2000-02-11 MX MXPA01012099A patent/MXPA01012099A/es not_active Application Discontinuation
  • 2000-02-11 EP EP00910669A patent/EP1181775B1/de not_active Expired - Lifetime
  • 2000-02-11 DE DE60006524T patent/DE60006524T2/de not_active Expired - Lifetime
  • 2000-02-11 WO PCT/EP2000/001119 patent/WO2000074237A1/en active IP Right Grant
  • 2000-02-11 JP JP2001500432A patent/JP2003501854A/ja not_active Withdrawn
  • 2000-11-02 US US09/980,220 patent/US6957053B1/en not_active Expired - Fee Related

Non-Patent Citations (1)

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